This invention relates generally to rotary, turn-to-set fastener devices and more particularly is directed to quarter turn fasteners operative to quickly secure and release two juxtaposed panels.
Fasteners of this type are well known in the fastening art and are typically configured to include a solid shank with a radially enlarged, generally circular, head with the lower region of the shank having a helical camming groove adapted to receive a wire element integrally formed in a retainer plate affixed below the lowermost panel. In operation, these retainer plates are preferably preassembled to the lowermost panel. The fastener is inserted through a pair of apertures in both panels and rotated a quarter turn so that the grooves lockingly and resiliently engage and compress the wire creating a clamped joint. Devices of this type are typically relatively expensive and obviously require a multipart system and often exhibit relatively high on and off torque to properly seat and/or remove the fastener from its locking position. A retainer plate for such a system must, in some manner, be preassembled to the lower panel.
Other disadvantages of this type of fastener and other prior art turn-to-set fasteners is the inability to preassemble the fastener within a top panel so that a plurality of such fasteners can be preassembled in one panel and all locked after a mating second panel is positioned over the fasteners.
Various plastic devices have been devised exhibiting quarter turn locking features, however none of these incorporate a significant resilient clamping feature.
Accordingly, it is a primary object of the present invention to provide a quarter turn fastener which incorporates features enabling it to be preassembled in a top panel in a particular radial orientation relative to an associated elongated aperture therein so that a plurality of such fasteners can be preassembled, followed by the locking of these fasteners, clamping two plates together after aligned elongated apertures of a second lower panel are assembled over the locking region.
Another object of the invention is to provide a quarter turn fastener which minimizes the material used to produce a firm but slightly flexible clamping joint.
Yet another object of the invention is to provide a fastening system with a particularly designed aperture in at least one of the panels cooperating with alignment and retention means in the fastener for preassembly purposes.
A particular advantage of the invention is a sheet metal fastener incorporating a plurality of spring forces which can be quickly applied to a pair of panels with a minimum of on or off torque.